As well known in the art, because valve heads of intake valves, or exhaust valves, for use in internal combustion engines are repeatedly brought into abutment against valve seats at a high speed, a high degree of wear resistance is required for the valve heads. As shown in FIG. 7, therefore, a highly wear-resistance material (e.g, a Co--Cr--W--C base alloy) is fillet-welded, at 3, FIG. 7, to a valve head 2 of a valve 1. The fillet-welded portion is then mechanically machined (e.g., ground) into a desired shape. Heretofore, such fillet welding to the valve head has been manually carried out by a worker using a welding rod of the Co--Cr--W--C base alloy while the valve is fixedly held on a holder.
Problems Solved by the Invention
The conventional fillet welding method, however, has a problem that because the fillet welding is manually performed by workers, the welded fillets are varied in thickness and position depending on the skill of the workers. Thus, quality of the fillet welding is not stable.
Also, in the conventional fillet welding method, fillet welding is manually carried out by workers who pick up, by hand, a valve blank, holds such valve blank on a holder, performs the fillet welding, and removes the valve from the holder after fillet welding. Productivity per unit time is extremely low.
To solve the above problems, it would be conceivable to employ a robot for supplying valve blanks and discharging product valves. But, because the valve blanks and the product valves each have a configuration defined by an umbrella-shaped valve head and a rod-shaped valve stem, which are joined together, there is a difficulty in handling them by a robot and risks that workpieces would be incorrectly held by handling means of the robot and slipped off from the handling means during transfer. The supply accuracy of workpieces to the holder would be poor.
Preferably, fillet-welded valves, hereinafter referred to as product valves, are sampled periodically (e.g., once per 100 valves) and the sampled product valves are subject to a destructive test, for example, by cutting the product valve, observing the cut section in enlarged scale, and checking the welded state.
To this end, workers must memorize, or record, the number of product valves which have been fillet welded. It is, however, unavoidable that the workers are apt to forget to sample the product valve or the sampling interval is varied, with a resultant difficulty in ensuring satisfactory quality of the fillet welding.
In view of the state of art described above, an object of the present invention is to provide a fillet welding apparatus by which high productivity can be achieved, valves can always be correctly held, and one of fillet-welded valves can be automatically sampled each time the predetermined number of valves are fillet-welded.
To solve the above problems, according to one embodiment of the present invention, there is provided a fillet welding apparatus for fillet-welding a different kind of material on valves heads of intake valves, or exhaust valves, for use in internal combustion engines, the apparatus being characterized in comprising valve blank stock means for storing valve blanks to be fillet-welded, a welding torch for performing fillet welding on a valve head of each of the valve blanks, valve blank holding means for holding the valve blank such that the valve head of the valve blank faces the welding torch, product valve stock means for storing product valves having been fillet-welded by the welding torch, and valve transfer means for transferring the valve blank from the valve blank stock means to the valve blank holding means, and for transferring the product valve from the valve blank holding means to the product valve stock means. The valve transfer means includes swing arm means mounted to be swingable about at least one point on the stationary side from the valve blank stock means to the valve blank holding means, then from the valve blank holding means to the product valve stock means, and then from the product valve stock means to the valve blank stock means, the swing arm means having chuck means attached to its distal end to grasp a valve stem of the valve blank or the product valve from both sides.
In the fillet welding apparatus according to the invention, a rotating member is rotatably attached to the distal end of the swing arm means, and a plurality of chuck means are attached to an outer peripheral portion of the rotating member.
In the fillet welding apparatus according to the invention, each of the chuck means comprises two abutting means capable of moving closer and away from each other, and drive means for moving the abutting means to come closer and away from each other. One of the two abutting members has two first V-shaped grooves which are brought into abutment against the valve stem of the valve blank or the product valve at two points spaced axially of the valve stem. The other of the two abutting members has a second groove which is brought into abutment against the valve stem at a point between the two first grooves.
In the fillet welding apparatus according to the invention, a sampling chute, for allowing a sample of the product valves to be dropped therethrough, is provided near the product valve stock means. Control means for the valve transfer means is provided to control the valve transfer means so that when the number of transfer cycles, in each of which the valve blank is transferred from the valve blank stock means to the valve blank holding means and the product valve is transferred from the valve blank holding means to the product valve stock means by the valve transfer means, reaches a predetermined number, the product valve transferred by the valve transfer means is supplied to the sampling chute.
With the fillet welding apparatus according to the present invention, the swing arm means of the valve transfer means is swung about at least one point on the stationary side toward the valve blank stock means so that the chuck means, attached to the distal end of the swing arm means, is directed to one of the valve blanks stored in the valve blank stock means. Next, the valve blank is held by being grasped, at its valve stem, by the chuck means laterally from both sides. In this condition, the swing arm means of the valve transfer means is swung about at least one point on the stationary side from the valve blank stock means toward the valve blank holding means. Then, the valve blank, held by the chuck means, is transferred to the valve blank holding means which holds the valve blank such that a valve head of the valve blank faces the welding torch, followed by fillet welding on the valve head. Next, a finished product valve is held by being grasped at its valve stem by the chuck means laterally from both sides, and is removed from the valve blank holding means. The swing arm means is swung about at least one point on the stationary side from the valve blank holding means toward the product valve stock means. When the product valve, grasped by the chuck means, is positioned to face the product valve stock means, the product valve is released from its grasped state by the chuck means to be stored in the product valve stock means. Then, the swing arm means is swung about at least one point on the stationary side from the product valve stock means toward the valve blank stock means. Subsequently and in a like manner, another valve blank is held by being grasped at its valve stem by the chuck means laterally from both sides, the swing arm means is swung toward the valve blank holding means, and the transferred valve blank is set to the valve blank holding means. Thus, transfer, setting and fillet welding of the valve blank, and removal and transfer of the product valve can be performed in successive steps.
With the fillet welding apparatus according to the present invention, the swing arm means of the valve transfer means is swung about at least one point on the stationary side, toward the valve blank stock means, to rotate the rotating member, attached to the distal end of the swing arm means, so that one of the plurality of chuck means, attached to the outer peripheral portion of the rotating member, is directed to one of the valve blanks stored in the valve blank stock means. Next, the valve blank is held by being grasped at its valve stem by the chuck means laterally from both sides. In this condition, the swing arm means of the valve transfer means is swung about at least one point on the stationary side from the valve blank stock means toward the valve blank holding means. Then, the valve blank, held by the chuck means, is transferred to the valve blank holding means which holds the valve blank such that a valve head of the valve blank faces the welding torch, followed by fillet welding on the valve head. Next, a finished product valve is held by being grasped at its valve stem by the chuck means laterally from both sides, and the rotating member is rotated to remove the product valve from the valve blank holding means. With the rotation of the rotating member, another valve blank grasped by the chuck means, other than the one grasping the product valve from both sides, is set to the valve blank holding means. Then, the swing arm means is swung about at least one point on the stationary side from the valve blank holding means toward the product valve stock means. When the product valve, grasped by the chuck means, is positioned to face the product valve stock means, the product valve is released from its grasped state by the chuck means to be stored in the product valve stock means. Then, the swing arm means is swung about at least one point on the stationary side from the product valve stock means toward the valve blank stock means. Subsequently and in a like manner, another valve blank is held by being grasped at its valve stem laterally from both sides by the one of the chuck means which are attached to the outer peripheral portion of the rotating member, and the swing arm means is swung toward the valve blank holding means. Further, by rotating the rotating member, the transferred valve blank is set to the valve blank holding means, and the product valve is removed from the valve blank holding means and transferred to the product valve stock means, as described above. Thus, transfer, setting and fillet welding of the valve blank, and removal and transfer of the product valve can be performed in successive steps.
With the fillet welding apparatus according to the present invention, the valve stem of the valve blank, or the product valve, is grasped by the chuck means from both sides. At this time, when the two abutting means of the chuck means are driven to come closer to each other, the two first V-shaped grooves of one of the two abutting members are brought into abutment against the valve stem of the valve blank, or the product valve, at two points spaced axially of the valve stem, and the second groove of the other abutting member is brought into abutment against the valve stem at a point between the two first grooves. With such an arrangement, the valve blank, or the product valve, is positively held at three points by the first grooves and the second groove of the two abutting members. As a result, it is possible to prevent the valve blank, or the product valve, from losing its correctly held state during transfer, prevent it from slipping off the chuck means, and further prevent a reduction in supply accuracy thereof to the valve blank holding means.
With the fillet welding apparatus of the present invention, when the number of transfer cycles, in each of which the valve blank is transferred from the valve blank stock means to the valve blank holding means and the product valve is transferred from the valve blank holding means to the product valve stock means by the valve transfer means, reaches a predetermined number, control means for the valve transfer means controls the valve transfer means so that the product valve transferred by the valve transfer means is supplied to the sampling chute. In other words, upon the predetermined number of transfer cycles being reached, the product valve is automatically sampled.